pt50 s2 q14

jlhero
Posts: 49
Joined: Mon Feb 02, 2009 11:52 pm

pt50 s2 q14

Postby jlhero » Sun Aug 28, 2011 5:16 pm

um...

the stem asks of a necessary assumption but the correct answer choice is a sufficient assumption.

the argument has only 1 gap and the gap is bridged perfectly by the correct answer choice.

i am confused.

y could a sufficient assumption be the correct answer choice?

should a necessary assumption only bridge the gap of an argument incompletely?

can someone explain it to me?

thanks~

jlhero
Posts: 49
Joined: Mon Feb 02, 2009 11:52 pm

Re: pt50 s2 q14

Postby jlhero » Mon Aug 29, 2011 1:32 am

someone please?

User avatar
suspicious android
Posts: 938
Joined: Tue Feb 09, 2010 4:54 pm

Re: pt50 s2 q14

Postby suspicious android » Mon Aug 29, 2011 2:50 am

Short answer, assumptions can be both necessary and sufficient for an argument's validity. This is not a super common quality for a correct answer on an assumption question, but it does happen. Being sufficient doesn't make it any more or less necessary, they are not mutually exclusive qualities.

Consider the following argument:

Joe is a Texan.
Therefore Joe is an American.

The assumption is obviously "All Texans are Americans", right? Well, that's clearly sufficient, with those two statements the conclusion must be true. However, this assumption is also necessary for the argument, since without it, we have no basis for the conclusion.

Basically if you are looking for a necessary assumption, an answer choice being sufficient should not affect your decision about its suitability.

jlhero
Posts: 49
Joined: Mon Feb 02, 2009 11:52 pm

Re: pt50 s2 q14

Postby jlhero » Mon Aug 29, 2011 10:52 am

thanks,

but can u consider this example?

A beer costs $2, and X has enough money to buy a beer.

if u assume X has exactly 2 dollars, it is a sufficient assumption but it is not a necessary assumption.

a necessary assumption would be something like, x has at least 1 dollar.

User avatar
KevinP
Posts: 1324
Joined: Sat Sep 26, 2009 8:56 pm

Re: pt50 s2 q14

Postby KevinP » Mon Aug 29, 2011 2:47 pm

jlhero wrote:thanks,

but can u consider this example?

A beer costs $2, and X has enough money to buy a beer.

if u assume X has exactly 2 dollars, it is a sufficient assumption but it is not a necessary assumption.

a necessary assumption would be something like, x has at least 1 dollar.


Correct in that if X has exactly 2 dollars, the condition is a sufficient, but not a necessary condition. This is attributed to the keyword exactly; X is not required to have exactly 2 dollars since X could just as well have 3 dollars.

However, if you have the condition that X has at least 2 dollars, then that is both a sufficient and a necessary condition.




Return to “LSAT Prep and Discussion Forum”

Who is online

Users browsing this forum: Baidu [Spider], Christinabruin and 3 guests